Investigations on the physical understanding of mobility in MOSFETs - from drift-diffusion to quasi-ballistic

This paper provides scattering matrix method to analyze the transport property in nanoscale MOSFETs. A unified mobility model with analytical expression is presented, which can cover the whole range from drift-diffusion to quasi-ballistic region. The inherent mobility reduction in MOSFETs with the shrinking of the channel length is extensively investigated from the theory and well agrees with the experiments, but the low-field free path is nearly constant. It is found that the reduction of measured mobility in nano-MOSFETs is only an apparent phenomenon. The relationship between the low-field mean free path ¿₀ and the driving current in nano-MOSFETs is discussed. The results indicate it is the ¿₀ instead of apparent mobility that determine the transport characteristics in nano-devices.